Fix error when jQuery is trying to do toLowerCase an empty array.

[glrodasz]

I updated the version of jQuery of an old app. This app have a plugin called jqGrid, and in the method "setCell" is possible pass an Array of properties (attributes) for set them in a cell. The code have a lot of this and the guy who implemented it time ago the code have a lot of empty arrays set. So when jquery-migrate try to do a toLowerCase() of an empty array it throws an error. I don't know if is the best fix but works for me.

[dmethvin]

An array has never been valid input to .attr() as far as I can tell. Allowing invalid inputs is beyond the scope of what this plugin does, and this patch won't work on all browsers anyway, so I am going to close this. If you can patch the plugin to work that would be great. Perhaps the original author would let you fork and maintain it?

[glrodasz]

ok, I will try! :D